Dear Dheeraj, your exit from the company closely followed the closure of the company. In that case, you could have been a little more cautious and approached this forum within a month of your exit. Now that the company is closed, issuing a backdated experience letter is not legally tenable.
Anyway, have you spoken to the MD of the company? What did he say? If he is avoiding your calls, then approach the Labour Officer under whose jurisdiction your company fell and explain your problem. Do not disclose to him that the company is now closed. Just provide him with the MD's name and number.
Please note that the Labour Officer is a government-appointed authority and is different from a labor lawyer. The latter is a professional who works in an individual capacity.
Thanks,
Dinesh Divekar